Marine propulsion unit

ABSTRACT

One of a pair of twin propeller drive shafts has an internal ring gear in mesh with a pinion on a first power shaft; and the other propeller drive shaft has a duplicate internal ring gear and is driven by means of a duplicate pinion which is secured to a second power shaft and axially spaced from said duplicate ring gear, and by means of a reverse idler having one gear section in mesh with the duplicate pinion and another gear section in mesh with the duplicate ring gear.

United States Patent [191 Benson, Jr.

[ Feb. 26,1974

[ 1 MARINE PROPULSION UNIT [75] Inventor:

[73] Assignee: Paragon Gears, Incorporated,

Taunton, Mass.

[22] Filed: Oct. 2, 1972 [211 App]. No.: 294,288

Carl I. Benson, Jr., Raynham, Mass.

[52] US. Cl. 74/413, 74/606 R [51] Int. Cl. F16h l/20, Fl6h 57/02 [58] Field of Search. 74/413, 325, 606 R, 200, 201,

[56] References Cited UNITED STATES PATENTS 3,234,808 2/1966 Nelson r 74/606 1,462,675 7/1923 Whittington.... 74/606 2,851,896 9/1958 Ordway t r 74/413 1,604,401 10/1926 Fisher 74/413 1,735,398 11/1929 Hoagland 74/421 1,774,618 9/1930 Thompson 74/413 2,230,604 2/1941 Ware 184/104 Primary Examiner-Al1an D. Herrmann Assistant ExaminerP. S. Lall Attorney, Agent, or Firm-James E. Nilles [57] ABSTRACT One of a pair of twin propeller drive shafts has an internal ring gear in mesh with a pinion on a first power shaft; and the other propeller drive shaft has a duplicate internal ring gear and is driven by means of a duplicate pinion which is secured to a second power shaft and axially spaced from said duplicate ring gear, and by means of a reverse idler having one gear section in mesh with the duplicate pinion and another gear section in mesh with the duplicate ring gear.

4 Claims, 5 Drawing Figures PATENIEI] FEB 2 8.197

sum 2 or 3 FIG.

PATENTEUFEBZB I974 I 3793.900

sum 3 or 3 FIG. 4

MARINE PROPULSION UNIT BACKGROUND OF THE INVENTION The invention has to do with power boats and it is concerned more particularly with a marine propulsion unit for use in twin propeller boats which are equipped with a separate internal combustion engine for each propeller.

Internal combustion engines are ordinarily made for one direction of rotation. For marine use most manufacturers have been making both one rotation and opposite rotation engines so that they can provide matched pairs for use in twin propeller power boats. However, the manufacture of opposite rotation engines is expensive due to special parts and tools required. Accordingly, the engine manufacturer looks to the transmission manufacturer to provide means for reversing rotation.

Conventionally, twin propeller power boats are equipped with two internal combustion engines, one of each rotation; two identical reversing mechanisms, one for each engine, and each operable to transmit engine power to an output shaft selectively in opposite directions; and with two speed reducing gearings, one between the output shaft of one reversing mechanism and a drive shaft for one of the propellers, and the other between the output shaft of the other reversing mechanism and a drive shaft for the other propeller. For practical reasons, it is usually required that the propellers of a twin propeller boat rotate in opposite directions. That is, with both engines running and both reversing mechanisms adjusted for drive in the same direction as engine rotation, one speed reducing gearing must drive its associated propeller shaft in one direction, and the other speed reducing gearing must rotate its associated propeller shaft in the opposite direction. Also, the speed reducing gearings must be matched; that is, they must provide exactly the same gear ratios.

In order to take care of the mentioned requirements of the speed reducing gearings, it has heretofore been suggested to use planetary gearings having coaxial power input and output shafts. Such planetary type speed reducing gearings, however, are often noisy and because of design considerations, matched pairs are limited to about 2:1 ratio. A further disadvantage of using planetary speed reducing gearings for oppositely rotating output shafts is that, as heretofore constructed, their gear ratios have not been made exactly identical.

Another known type of speed reducing gearing which has heretofore been used in power boats for transmitting driving power from the output shaft of a reversing mechanism to a propeller shaft is shown in US. Pat. No. 2,230,604, issued Feb. 4, 1941 to W.C. Ware for Reverse and Reduction Gearing. The principal components of the reducing gearing shown in that patent are a pinion on the output shaft of a reversing mechanism and an internally toothed ring gear on the propeller drive shaft in mesh with the pinion. This gear arrangement requires mounting of the propeller drive shaft on an axis extending parallel to and offset transversely from the axis of the reversing mechanism output shaft.

A ring gear type speed reducing mechanism such as shown in the Ware patent, wherein a drive pinion meshes directly with an internal ring gear, provides for unidirectional rotation of its input and output shafts, and a twin propeller boat equipped with two engines of the same rotation and using such a speed reducing mechanism for one of the propellers requires another speed reducing mechanism for the other propeller which rotates the second propeller at the same speed as the first propeller but in the opposite direction.

In order to take care of the requirement for reverse rotation of the second propeller shaft at the same speed as the first propeller shaft, it has heretofore been suggested to equip the input and output shafts of the second speed reducing gearing with a pinion and a ring gear the same as those in the first speed reducing gear, but to shorten the offset between the pinion and ring gear shafts so as to get the pinion and ring gear of the second reduction gearing out of mesh at the top, and to add a reversing idler at the bottom. This arrange ment has the disadvantage that the engines must be installed at different heights which is undesirable for practical reasons.

SUMMARY OF THE INVENTION Generally, it is an object of the invention to provide an improved marine propulsion unit which avoids the hereinbefore outlined shortcomings and disadvantages of the prior art.

More specifically, it is an object of the invention to provide an improved marine propulsion unit for use on twin propeller power boats which are equipped with separate driving engines rotating in the same direction, and which require a non-reversing speed reducing mechanism for one of the propellers and a reversing speed reducing mechanism for the other propeller.

A further object of the invention is to provide an improved marine propulsion unit of the mentioned character which incorporates a reversing speed reducing mechanism of the internal ring gear type and which may readily be converted into a non-reversing speed reducing mechanism affording exactly the same gear ratio and offset between the input and output shafts as the original reversing speed reducing mechanism.

A further object of the invention is to provide a convertible speed reducing mechanism of the mentioned character which utilizes a number of major components which require no structural changes or replacement when the mechanism is converted from the reversing type to the non-reversing type, and vice versa. For example, an entire assembly comprising a housing section, the propeller drive shaft, bearings and ring gear may be the same for the reversing speed reducing mechanism and for the converted non-reversing mechanism, and also the same driving pinion may be used for the reversing as well as for the converted non-reversing speed reducing mechanism embodying the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and advantages will become more fully apparent from the following description of a preferred embodiment of the invention and the accompanying drawings wherein:

FIG. 1 is a schematic plan view of the rear part of a twin propeller power boat;

FIG. 2 is a section taken on line 22 of FIG. 1;

FIG. 3 is an enlarged sectional view on line 3-3 of FIG. 1;

FIG. 4 is an enlarged sectional view on line 4-4 of FIG. 1; and

FIG. is a diagrammatic end view on line 5-5 of FIG. 3, but on a reduced scale.

DETAILED DESCRIPTION The power boat shown in FIGS. 1 and 2 comprises a hull 1; starboard and port engines 2 and 3; starboard and port propulsion units 4 and 6; starboard and port propeller shafts 7 and 8; and starboard and port propellers, the starboard propeller being shown in FIG. 2 and designated by the reference numeral 9, and the port propeller (not shown) being an opposite hand duplicate of the starboard propeller 9.

The engines 2 and 3 are duplicate internal combustion engines of conventional construction and are mounted within the hull 1 on a common rearwardly and downwardly slanting level as indicated by the dash dotted line 11.

The starboard propulsion unit as shown in FIG. 3 comprises two principal components, namely a forward and reverse driving mechanism 12 and a reversing speed reducing mechanism 13 in rear of the forward and reverse driving mechanism 12.

Generally, the forward and reverse driving mechanism l2 conforms with well-known principles of construction and operation. It comprises a housing body 14 having a front cover 16, a rear cover 17 and a top cover 18. A planetary gear mechanism within the housing body 14 comprises a sun gear 19 on a power input shaft 21, a spider 22 mounting planet pinions 23 and 24, and a driven pinion 26 on a power output shaft 27. As usual, the planet pinion 23 shown in FIG. 3 meshes with a companion planet pinion, not shown, which like the pinion 24 meshes with the driven pinion 26; and the planet pinion 24 shown in FIG. 3 meshes with a companion planet pinion, not shown, which like the pinion 23 meshes with the sun gear 19. A hydraulically operated multiple disc clutch 28 is operatively interposed between the spider 22 and the output shaft 27, and a hydraulically operated brake band 29 is placed around a drum portion of the spider 22. A hydraulic circuit for operating the clutch 28 and brake 29 includes a rotatable control valve 31 having a handle 32, which in one position causes engagement of the clutch 28 and simultaneous release of the brake 29, and in another position causes setting of the brake 29 and simultaneous disengagement of the clutch 28. When the clutch is engaged and the brake released, engine torque applied to the shaft 21 is transmitted from the sun gear 19 through the pairs of intermeshing planet pinions 23 and 24 to the driven pinion 26 on the shaft 27. The resulting torque reaction on the spider 22 tends to rotate the latter relative to the shaft 27, but such rotation of the spider is precluded by the engaged clutch 28. That means, the planetary gearing is locked up, and driving torque applied to the input shaft 21 by the engine 2 causes the output shaft 27 to rotate in unison with the input shaft 21. On the other hand, when the clutch 28 is released I in the opposite direction and at substantially the same speed as the input shaft.

The port propulsion unit 6 incorporates a duplicate of the forward and reverse mechanism 12 shown in FIG. 3.

Referring now to the speed reducing reversing mechanism 13 shown in FIG. 3, the following should be noted. The output shaft 27 of the forward and reverse mechanism 12 is supported by a ball bearing 33 in the rear cover 17 which is detachably secured to the housing body 14. The rear cover 17 is further provided with a fixed rearwardly extending stub shaft 34 and with a rearwardly projecting wall structure including an end plate 36 in supporting engagement with the rear end of the stub shaft 34. The output shaft 27 of the forward and reverse mechanism has an integral pinion 37 in rear of the ball bearing 33, and the stub shaft 34 mounts a reverse idler comprising a forward gear section 38 in mesh with the pinion 37 and an integral rearward gear section 39 in axially overhanging relation to the pinion 37. The idler gear sections 38 and 39 have the same pitch, pitch diameter and tooth profile.

The pinion 37 and reverse idler section 38 are surrounded by an annular housing section 41 which is detachably secured to the cover plate 17 of the forward and reverse mechanism 12. Detachably secured to the rear of the annular housing section 41 is a cup shaped housing section 42 which supports a propeller drive shaft 43 in a pair of conical roller bearings 44, 46 at a substantial rearward spacing from the pinion 37. The roller bearings 44, 46 support the shaft 43 in the housing 42 on an axis which in the installed position of the housing 42 as shown in FIG. 3, extends parallel to the axis of the pinion 37 but is offset downwardly therefrom by a distance X as shown in FIG. 5. The shaft 43 has at its inner end an integral ring gear 47 with internal teeth axially overlapping and meshing with the rearward reverse idler gear section 39. As a result of the cooperative relation between the pinion 37 and the forward reverse idler section 38, and of the cooperative relation between the rearward reverse idler section 39 and ring gear 47, rotation of the pinion 37 in one direction causes rotation of the propeller drive shaft 43 at a reduced speed in the opposite direction, the reduction ratio being the gear ratio between the pinion 37 and the ring gear 47.

The port propulsion unit 6 in FIG. 1 incorporates, as stated, a duplicate of the forward and reverse mechanism 12 shown in FIG. 3, and it also incorporates a non--reversing speed reduction unit as shown in FIG. 4. Comparing FIG. 4 with FIG. 3, it will be noted that the entire assembly comprising the cup shaped housing 42, propeller drive shaft 43, bearings 44, 46 and ring gear 47 shown in FIG. '3 is duplicated in FIG. 4. Also, the pinion 37 and the ball bearing 33 shown in FIG. 3 are duplicated in FIG. 4. However, in FIG. 4 the housing section 41 and the reversing idlers 38 and 39 are omitted, and the cup shaped housing section 42 is detachably secured to a modified cover plate 17 of the forward and reverse mechanism 12. The forward shift of the cup shaped housing 42 and enclosed parts from the position shown in FIG. 3 to the position shown in FIG. 4 brings the ring gear 47 into direct mesh with the pinion 37, and driving torque applied to the pinion 37 in FIG. 4 in one direction will therefore cause rotation of the propeller shaft 43 in FIG. 4 at a reduced speed in the same direction. The reduction ratio of the speed reducing mechanism shown in FIG. 4 is the same as the reduction ratio of the speed reducing mechanism shown in FIG. 3, and the offset X between the axes of the pinion 37 and propeller drive shaft 43 in FIG. 4 is the same as the offset X between the axes of the pinion 37 and propeller drive shaft in FIG. 3.

In FIG. 1, the propeller shaft 8 is somewhat longer than the propeller shaft 7 in order to make up for the shortening of the propulsion unit 6 by the forward shift of the housing section 42 and enclosed parts.

A characterizing feature of the reversing speed reducing mechanism 13 shown in FIG. 3 is the fact that the pitch radii of the reverse idler sections 38 and 39 are the same as the offset X between the axes of the pinion 37 and the propeller drive shaft 43. The identity of the offset X and the pitch radii of the reverse idler sections 38, 39 may readily be shown as follows.

As shown in FIG. 5:

2Rg=2R +2Rp 1 and Rg=X+Rp (2) Equating Rg of equation (1) with Rg of equation (2) results in R, Rp X Rp which resolves into The reduction ratio Rg/Rp is not limited by design considerations and in accordance with the invention R, will have to be equal to X for any selected reduction ra- 00.

In summary, the marine propulsion unit incorporating the present invention comprises a driving shaft and a driven shaft which are rotatable on parallel axes at a predetermined transverse spacing from each other, and which in the illustrated embodiment of the invention are represented by the shafts 27 and 43, respectively. Speed reducing gearing connects the driving shaft 27 in drive reversing relation with the driven shaft 43 and comprises a drive pinion secured to the driving shaft, a first idler gear section in mesh with said pinion and having a pitch radius equal to said shaft spacing; a second idler gear section identical to and coaxial with said first idler gear section connected to the latter for rotation therewith in axially overchanging relation to said drive pinion; and a ring gear secured to said driven shaft having internal teeth in mesh with said second gear section on a pitch radius equal to the sum of said shaft spacing and the pitch radius of said drive pinion. In the illustrated embodiment of the invention, the pinion 37 represents the mentioned drive pinion; the gear sections 38, 39 represent the mentioned first and sec ond idler gear sections, and the driven gear 43 represents the mentioned ring gear.

A forward mounting structure which rotatably supports the mentioned driving shaft is represented in the illustrated embodiment of the invention by the housings 14, 16, 17 of the forward and reverse driving mechanism 12; a rearward housing structure which rotatably mounts the mentioned driven shaft and is spaced in the axial direction of the latter form the forward mounting structure is represented by the housing section 42; and an adapter structure which is removably positioned'between said mounting and housing structures and which rotatably supports the mentioned first and second idler gear sections is represented by the housing section 41.

What is claimed is:

1. A marine propulsion unit comprising a driving shaft and a driven shaft relatively rotatable on parallel axes at a predetermined transverse spacing from each other; and speed reducing gearing connecting said driving shaft in drive reversing relation with said driven shaft; said speed reducing gearing comprising a drive pinion secured to said driving shaft; a first idler gear section in mesh with said pinion and having a pitch radius equal to said shaft spacing; a second idler gear section identical to and coaxial with said first idler gear section connected to the latter for rotation therewith in axially overhanging relation to said drive pinion; and a ring gear secured to said driven shaft having internal teeth in mesh with said second idler gear section on a pitch radius equal to the sum of said shaft spacing and the pitch radius of said drive pinion.

2. A marine propulsion unit as set forth in claim 1 and further comprising a forward mounting structure rotatably supporting said driving shaft; a rearward housing structure rotatably mounting said driven shaft and spaced in the axial direction of the latter from said forward mounting structure; an adapter structure removably positioned between said mounting and housing structures and rotatably supporting said first and second gear sections.

3. A marine propulsion unit as set forth in claim 2 wherein said rearward housing structure is adapted for direct connection to said forward mounting structure upon removal of said adapter structure, so as to bring said ring gear into mesh with said drive pinion.

4. A marine propulsion unit comprising a forward housing structure mounting a rotatable drive pinion in rearwardly overhanging relation thereto and enclosing power transmitting gearing selectively operable to rotate said pinion in opposite directions; an adapter structure detachably secured to the rear of said forward housing structure and mounting an idler gear on an axis extending parallel to and spaced from the axis of said drive pinion; said idler gear having a forward section in mesh with said drive pinion and an identical rearward section in axially overhanging relation to said pinion; a rearward housing structure detachably secured to the rear of said adapter structure and mounting a driven shaft on an axis extending parallel to the axis of said drive pinion and spaced transversely therefrom a distance equal to the pitch radius of said idler gear; and a ring gear secured within said rearward housing structure to said driven shaft and having internal teeth in mesh with said rearward section of said idler gear on a pitch radius equal to said pitch radius of said idler gear plus the pitch radius of said drive pinion. 

1. A marine propulsion unit comprising a driving shaft and a driven shaft relatively rotatable on parallel axes at a predetermined transverse spacing from each other; and speed reducing gearing connecting said driving shaft in drive reversing relation with said driven shaft; said speed reducing gearing comprising a drive pinion secured to said driving shaft; a first idler gear section in mesh with said pinion and having a pitch radius equal to said shaft spacing; a second idler gear section identical to and coaxial with said first idler gear section connected to the latter for rotation therewith in axially overhanging relation to said drive pinion; and a ring gear secured to said driven shaft having internal teeth in mesh with said second idler gear section on a pitch radius equal to the sum of said shaft spacing and the pitch radius of said drive pinion.
 2. A marine propulsion unit as set forth in claim 1 and further comprising a forward mounting structure rotatably supporting said driving shaft; a rearward housing structure rotatably mounting said driven shaft and spaced in the axial direction of the latter from said forward mounting structure; an adapter structure removably positioned between said mounting and housing structures and rotatably supporting said first and second gear sections.
 3. A marine propulsion unit as set forth in claim 2 wherein said rearward housing structure is adapted for direct connection to said forward mounting structure upon removal of said adapter structure, so as to bring said ring gear into mesh with said drive pinion.
 4. A marine propulsion unit comprising a forward housing structure mounting a rotatable drive pinion in rearwardly overhanging relation thereto and enclosing power transmitting gearing selectively operable to rotate said pinion in opposite directions; an adapter structure detachably secured to the rear of said forward housing structure and mounting an idler gear on an axis extending parallel to and spaced from the axis of said drive pinion; said idler gear havinG a forward section in mesh with said drive pinion and an identical rearward section in axially overhanging relation to said pinion; a rearward housing structure detachably secured to the rear of said adapter structure and mounting a driven shaft on an axis extending parallel to the axis of said drive pinion and spaced transversely therefrom a distance equal to the pitch radius of said idler gear; and a ring gear secured within said rearward housing structure to said driven shaft and having internal teeth in mesh with said rearward section of said idler gear on a pitch radius equal to said pitch radius of said idler gear plus the pitch radius of said drive pinion. 